A long-term NIDDK study reports that keeping blood glucose (sugar) as close to normal as possible for an average of 6.5 years early in the course of type 1 diabetes reduces cardiovascular (heart) disease for up to 30 years. The landmark Diabetes Control and Complications Trial (DCCT) began in 1983. The DCCT randomly assigned half its participants to an intensive blood glucose management regimen designed to keep blood glucose levels as close to normal as safely possible, and half to the less-intensive conventional treatment at the time. When DCCT ended in 1993, it was clear that intensive management had significantly reduced eye, nerve, and kidney complications, but at that time the participants were too young to determine their rates of cardiovascular disease. All DCCT participants were taught the intensive management regimen and invited to join the Epidemiology of Diabetes Interventions and Complications (EDIC) study. EDIC continued to monitor DCCT/EDIC participants’ health, and overall blood glucose management has since been similar in both DCCT treatment groups.

To study the long-term effects of the different treatments tested in the DCCT, researchers examined differences in cardiovascular problems, which can take many years to develop, between the former intensive and conventional treatment groups. After an impressive average 30-year follow-up, DCCT/EDIC researchers found that those who practiced intensive blood glucose management during the DCCT still had significantly reduced cardiovascular disease compared to those who did not, despite having similar blood glucose management for 20 years after the DCCT ended. Compared to the former conventional treatment group, the former intensive management group had a 30 percent reduced incidence of cardiovascular disease and 32 percent fewer major cardiovascular events (such as non-fatal heart attack, stroke, or death from cardiovascular disease), after 30 years of follow-up. These results were similar for both men and women who participated in the studies. However, the beneficial effects of intensively managing blood glucose during the DCCT appeared to be wearing off over time. Previously, after 20 years of follow-up, DCCT/EDIC researchers reported that the former intensive treatment group had a 42 percent reduced risk of cardiovascular disease compared to the former conventional treatment group. After 30 years of follow-up, that number had fallen to 30 percent. Even with this reduction in protection, these new data show that a finite period of near-normal blood glucose management early in the course of type 1 diabetes can have substantial beneficial effects on cardiovascular health for up to 30 years. Overall, this finding adds to DCCT/EDIC’s decades of evidence demonstrating how people with type 1 diabetes can dramatically reduce their risk for complications later in life by practicing early, intensive blood glucose management.